Ophthalmoscopes are commonly known medical diagnostic instruments used to perform routine examinations of the eye of a patient during a primary physician's visit. Due to their relatively low cost, these instruments are commonly found in the physician's office, hospitals and urgent care medical facilities. A typical ophthalmoscope is defined by an instrument head that is attached to the upper end of a handle portion, enabling the instrument to be relatively compact and capable of being held for use in a single hand of the caregiver. The handle portion retains a source of power (e.g., a plurality of rechargeable batteries) for energizing a contained light source, such as an incandescent lamp or at least one LED, in order to provide sufficient light to the intended target (i.e., the eye), through a distal end of the instrument head. An optical or imaging system contained within the instrument head images the illuminated retina of the eye and directs that image to either an eyepiece or an electronic imaging element, which is disposed at the proximal end of the instrument head.
Fundus cameras, such as described by EP 1 138 255 A1, are a much more sophisticated diagnostic apparatus, as compared to ophthalmoscopes, that are also used for measuring and determining various conditions involving the eye. These latter devices are quite prohibitive in cost, as compared to typical ophthalmoscopes, and can often easily exceed $25,000. The optical systems incorporated in fundus cameras are considerably more intricate and complex than those used in ophthalmoscopes and are also much larger, typically requiring a patient to utilize a chin rest or similar configuration for purposes of stability when conducting an examination. Advantageously, these instruments are configured to provide a field of view of at least 30 to 40 degrees relative to a target of interest (i.e., the eye), which adds significant functionality and capability as compared to direct ophthalmoscopes, the latter usually having a more restricted field of view of only about 5 degrees. Having a larger field of view is essential for enabling more comprehensive diagnoses, such as diabetic retinopathy, to be reliably conducted. Diabetic retinopathy often has no early warning signs, but first stages can be detected by fundus photography in which microaneurysms (microscopic blood-filled bulges in the artery walls), as well as retinal ischemia (blocked or narrowing retinal blood vessels) indicative of the lack of blood flow can be readily and proactively detected.
Given the present state of healthcare reform, a general need exists to provide an eye viewing device, such as an ophthalmoscope, that can reliably provide a larger field of view in order to permit more comprehensive eye examinations to be conducted, but in lieu of a fundus camera.
To that end, there have been numerous attempts to design diagnostic instruments that enable a caregiver to view more of the fundus of the eye. The majority of these attempts has been realized, but by means of scanning the area of interest and not directly viewing the desired area all at once and/or requiring medication to also dilate the pupil of the eye. Pupil dilation creates a level of inconvenience and discomfort for the patient.
More recently, Applicants have developed a digital ophthalmoscope with a contained imaging system that is capable of producing about a 25 degree field of view, using panoramic imaging of the retina. In one version, a smartphone is mechanically supported to the rear of an instrument housing with the imager of the smartphone being positioned in alignment with the contained optical assembly of the instrument or in which the optical assembly is augmented to divert an image to the portable electronic device in order to directly receive captured images.
Still further, it would be advantageous to provide an ophthalmic instrument that provides greater versatility in regard to operation when used in conjunction with a portable electronic device, such as a smartphone or a tablet PC.